Blind decoding for an enhanced physical downlink control channel (EPDCCH)

ABSTRACT

Technology for a user equipment (UE) configured for blind decoding downlink control information (DCI) from an enhanced physical downlink control channel (EPDCCH) is disclosed. The UE can receive, from a base station, the EPDCCH that includes the DCI. The UE can attempt one or more times to decode the DCI from enhanced control channel elements (ECCE) of the EPDCCH from physical resource block (PRB) region candidates in a PRB set using a selected set of enhanced resource element group (EREG) index maps for the ECCE until the DCI is successfully decoded.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/374,623 filed Dec. 9, 2016, which is a continuation of U.S. patentapplication Ser. No. 14/882,289 filed Oct. 13, 2015, which is acontinuation of U.S. patent application Ser. No. 13/931,102 filed Jun.28, 2013, which claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/721,436 filed Nov. 1, 2012, and U.S. ProvisionalPatent Application Ser. No. 61/707,784 filed Sep. 28, 2012, and U.S.Provisional Patent Application Ser. No. 61/719,241, filed Oct. 26, 2012,all of which are hereby incorporated by reference in their entirety.

BACKGROUND

Wireless mobile communication technology uses various standards andprotocols to transmit data between a node (e.g., a transmission stationor a transceiver node) and a wireless device (e.g., a mobile device).Some wireless devices communicate using orthogonal frequency-divisionmultiple access (OFDMA) in a downlink (DL) transmission and singlecarrier frequency division multiple access (SC-FDMA) in an uplink (UL)transmission. Standards and protocols that use orthogonalfrequency-division multiplexing (OFDM) for signal transmission includethe third generation partnership project (3GPP) long term evolution(LTE), the Institute of Electrical and Electronics Engineers (IEEE)802.16 standard (e.g., 802.16e, 802.16m), which is commonly known toindustry groups as WiMAX (Worldwide interoperability for MicrowaveAccess), and the IEEE 802.11 standard, which is commonly known toindustry groups as WiFi.

In 3GPP radio access network (RAN) LTE systems, the node can be acombination of Evolved Universal Terrestrial Radio Access Network(E-UTRAN) Node Bs (also commonly denoted as evolved Node Bs, enhancedNode Bs, eNodeBs, or eNBs) and Radio Network Controllers (RNCs), whichcommunicate with the wireless device, known as a user equipment (UE).The downlink (DL) transmission can be a communication from the node(e.g., eNodeB) to the wireless device (e.g., UE), and the uplink (UL)transmission can be a communication from the wireless device to thenode.

In LTE, data can be transmitted from the eNodeB to the UE via a physicaldownlink shared channel (PDSCH). A physical downlink control channel(PDCCH) can be used to transfer downlink control information (DCI) thatinforms the UE about resource allocations or scheduling related todownlink resource assignments on the PDSCH, uplink resource grants, anduplink power control commands. The PDCCH can be transmitted prior thePDSCH in each subframe transmitted from the eNodeB to the UE.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the disclosure will be apparent from thedetailed description which follows, taken in conjunction with theaccompanying drawings, which together illustrate, by way of example,features of the disclosure; and, wherein:

FIG. 1 illustrates a diagram of radio frame resources (e.g., a resourcegrid) for a downlink (DL) transmission including a legacy physicaldownlink control channel (PDCCH) in accordance with an example;

FIG. 2 illustrates a diagram of various component carrier (CC)bandwidths in accordance with an example;

FIG. 3 illustrates a diagram of enhanced physical downlink controlchannel (EPDCCH) and physical downlink shared channel (PDSCH)multiplexing in accordance with an example;

FIG. 4 illustrates a diagram of four enhanced control channel elements(ECCE) in one physical resource block (PRB) pair showing an enhancedresource element group (EREG) index for each resource element (RE) inaccordance with an example;

FIG. 5 illustrates an example for aggregation level (AL) ambiguity fordistributed enhanced physical downlink control channel (EPDCCH) inaccordance with an example;

FIG. 6 illustrates an example for aggregation level (AL) ambiguity in auser equipment's (UE's) blind decoding in accordance with an example;

FIG. 7A illustrates a diagram of aggregation level (AL) specificfrequency first mapping for AL 2 in accordance with an example;

FIG. 7B illustrates a diagram of aggregation level (AL) specificfrequency first mapping for AL 1 in accordance with an example;

FIG. 8 illustrates a flow diagram for enhanced physical downlink controlchannel (EPDCCH) processing at a node with aggregation level (AL)specific phase shifting in accordance with an example;

FIG. 9 illustrates a flow diagram for enhanced physical downlink controlchannel (EPDCCH) processing at a node with aggregation level (AL)specific scrambling of downlink control information (DCI) in accordancewith an example;

FIG. 10 illustrates a flow diagram for enhanced physical downlinkcontrol channel (EPDCCH) processing at a node with an interleaver afterrate matching in accordance with an example;

FIG. 11 illustrates a flow diagram for enhanced physical downlinkcontrol channel (EPDCCH) processing at a node with an interleaver aftermodulation in accordance with an example;

FIG. 12 depicts a flow chart of a method for blind decoding downlinkcontrol information (DCI) from an enhanced physical downlink controlchannel (EPDCCH) in accordance with an example;

FIG. 13 depicts functionality of computer circuitry of a node operablefor mapping resource elements (RE) to enhanced control channel elements(ECCE) of an enhanced physical downlink control channel (EPDCCH) basedon an aggregation level (AL) in accordance with an example;

FIG. 14 illustrates a block diagram of a node (e.g., eNB) and wirelessdevice (e.g., UE) in accordance with an example; and

FIG. 15 illustrates a diagram of a wireless device (e.g., UE) inaccordance with an example.

Reference will now be made to the exemplary embodiments illustrated, andspecific language will be used herein to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended.

DETAILED DESCRIPTION

Before the present invention is disclosed and described, it is to beunderstood that this invention is not limited to the particularstructures, process steps, or materials disclosed herein, but isextended to equivalents thereof as would be recognized by thoseordinarily skilled in the relevant arts. It should also be understoodthat terminology employed herein is used for the purpose of describingparticular examples only and is not intended to be limiting. The samereference numerals in different drawings represent the same element.Numbers provided in flow charts and processes are provided for clarityin illustrating steps and operations and do not necessarily indicate aparticular order or sequence.

Example Embodiments

An initial overview of technology embodiments is provided below and thenspecific technology embodiments are described in further detail later.This initial summary is intended to aid readers in understanding thetechnology more quickly but is not intended to identify key features oressential features of the technology nor is it intended to limit thescope of the claimed subject matter.

The communication of data on the physical downlink shared channel(PDSCH) can be controlled via a control channel, referred to as aphysical downlink control channel (PDCCH). The PDCCH can be used fordownlink (DL) and uplink (UL) resource assignments, transmit powercommands, and paging indicators. The PDSCH scheduling grant can bedesignated to a particular wireless device (e.g., UE) for dedicatedPDSCH resource allocation to carry UE-specific traffic, or the PDSCHscheduling grant can be designated to all wireless devices in the cellfor common PDSCH resource allocation to carry broadcast controlinformation such as system information or paging.

In one example, the PDCCH and PDSCH can represent elements of a radioframe structure transmitted on the physical (PHY) layer in a downlinktransmission between a node (e.g., eNodeB) and the wireless device(e.g., UE) using a generic 3GPP long term evolution (LTE) framestructure, as illustrated in FIG. 1.

FIG. 1 illustrates a downlink radio frame structure type 1. In theexample, a radio frame 100 of a signal used to transmit the data can beconfigured to have a duration, Tf, of 10 milliseconds (ms). Each radioframe can be segmented or divided into ten subframes 110 i that are each1 ms long. Each subframe can be further subdivided into two slots 120 aand 120 b, each with a duration, Tslot, of 0.5 ms. The first slot (#0)120 a can include a legacy physical downlink control channel (PDCCH) 160and/or a physical downlink shared channel (PDSCH) 166, and the secondslot (#1) 120 b can include data transmitted using the PDSCH.

Each slot for a component carrier (CC) used by the node and the wirelessdevice can include multiple resource blocks (RBs) 130 a, 130 b, 130 i,130 m, and 130 n based on the CC frequency bandwidth. The CC can have acarrier frequency having a bandwidth and center frequency. Each subframeof the CC can include downlink control information (DCI) found in thelegacy PDCCH. The legacy PDCCH in the control region can include one tothree columns of the first OFDM symbols in each subframe or physical RB(PRB), when a legacy PDCCH is used. The remaining 11 to 13 OFDM symbols(or 14 OFDM symbols, when legacy PDCCH is not used) in the subframe maybe allocated to the PDSCH for data (for short or normal cyclic prefix).

The control region can include physical control format indicator channel(PCFICH), physical hybrid automatic repeat request (hybrid-ARQ)indicator channel (PHICH), and the PDCCH. The control region has aflexible control design to avoid unnecessary overhead. The number ofOFDM symbols in the control region used for the PDCCH can be determinedby the control channel format indicator (CFI) transmitted in thephysical control format indicator channel (PCFICH). The PCFICH can belocated in the first OFDM symbol of each subframe. The PCFICH and PHICHcan have priority over the PDCCH, so the PCFICH and PHICH are scheduledprior to the PDCCH.

Each RB (physical RB or PRB) 130 i can include 12-15 kHz subcarriers 136(on the frequency axis) and 6 or 7 orthogonal frequency-divisionmultiplexing (OFDM) symbols 132 (on the time axis) per slot. The RB canuse seven OFDM symbols if a short or normal cyclic prefix is employed.The RB can use six OFDM symbols if an extended cyclic prefix is used.The resource block can be mapped to 84 resource elements (REs) 140 iusing short or normal cyclic prefixing, or the resource block can bemapped to 72 REs (not shown) using extended cyclic prefixing. The RE canbe a unit of one OFDM symbol 142 by one subcarrier (i.e., 15 kHz) 146.

Each RE can transmit two bits 150 a and 150 b of information in the caseof quadrature phase-shift keying (QPSK) modulation. Other types ofmodulation may be used, such as 16 quadrature amplitude modulation (QAM)or 64 QAM to transmit a greater number of bits in each RE, or bi-phaseshift keying (BPSK) modulation to transmit a lesser number of bits (asingle bit) in each RE. The RB can be configured for a downlinktransmission from the eNodeB to the UE, or the RB can be configured foran uplink transmission from the UE to the eNodeB.

Each wireless device may use at least one bandwidth. The bandwidth maybe referred to as a signal bandwidth, carrier bandwidth, or componentcarrier (CC) bandwidth, as illustrated in FIG. 2. For example, the LTECC bandwidths can include: 1.4 MHz 310, 3 MHz 312, 5 MHz 314, 10 MHz316, 15 MHz 318, and 20 MHz 320. The 1.4 MHz CC can include 6 RBscomprising 72 subcarriers. The 3 MHz CC can include 15 RBs comprising180 subcarriers. The 5 MHz CC can include 25 RBs comprising 300subcarriers. The 10 MHz CC can include 50 RBs comprising 600subcarriers. The 15 MHz CC can include 75 RBs comprising 900subcarriers. The 20 MHz CC can include 100 RBs comprising 1200subcarriers.

The data carried on the PDCCH can be referred to as downlink controlinformation (DCI). Multiple wireless devices can be scheduled in onesubframe of a radio frame. Therefore, multiple DCI messages can be sentusing multiple PDCCHs. The DCI information in a PDCCH can be transmittedusing one or more control channel elements (CCE). A CCE can be comprisedof a group of resource element groups (REGs). A legacy CCE can includeup to nine REGs. Each legacy REG can be comprised of four resourceelements (REs). Each resource element can include two bits ofinformation when quadrature modulation is used. Therefore, a legacy CCEcan include up to 72 bits of information. When more than 72 bits ofinformation are needed to convey the DCI message, multiple CCEs can beemployed. The use of multiple CCEs can be referred to as an aggregationlevel. In one example, the aggregation levels can be defined as 1, 2, 4or 8 consecutive CCEs allocated to one legacy PDCCH.

The legacy PDCCH can create limitations to advances made in other areasof wireless communication. For example, mapping of CCEs to subframes inOFDM symbols can typically be spread over the control region to providefrequency diversity. However, no beam forming diversity may be possiblewith the current mapping procedures of the PDCCH. Moreover, the capacityof the legacy PDCCH may not be sufficient for advanced controlsignaling.

To overcome the limitations of the legacy PDCCH, an enhanced PDCCH(EPDCCH) can use the REs in an entire PRB or PRB pair (where a PRB paircan be two contiguous PRBs using the same subcarrier's subframe),instead of just the first one to three columns of OFDM symbols in afirst slot PRB in a subframe as in the legacy PDCCH. Accordingly, theEPDCCH can be configured with increased capacity to allow advances inthe design of cellular networks and to minimize currently knownchallenges and limitations.

Unlike the legacy PDCCH, the EPDCCH can be mapped to the same REs orregion in a PRB as the PDSCH, but in different PRBs. In an example, thePDSCH and the EPDCCH may not be multiplexed within a same PRB (or a samePRB pair). Thus if one PRB (or one PRB pair) contains an EPDCCH, theunused REs in the PRB (or PRB pair) may be blanked, since the REs maynot be used for the PDSCH. The EPDCCH can be localized (e.g., localizedEPDCCH) or distributed (e.g., distributed EPDCCH). Localized EPDCCH canrefer to the entire EPDCCH (e.g., EREGs or ECCEs) within the PRB pair.Distributed EPDCCH can refer to EPDCCH (e.g., EREGs or ECCEs) spreadover plurality of PRB pairs.

Blind decoding can be used to detect a UE's DCI, including the DCItransmitted in the legacy PDCCH. The UE may only be informed of thenumber of OFDM symbols within the control region of a subframe and maynot be provided with an exact location of the UE's corresponding PDCCH.The PDCCH or EPDCCH can provide control information to multiple UEs in acell for each subframe k. The UE can perform blind decoding since the UEmay be aware of the detailed control channel structure, including thenumber of control channels (CCHs) and the number of control channelelements (CCEs) to which each control channel is mapped. Multiple PDCCHscan be transmitted in a single subframe k which may or may not berelevant to a particular UE. Because the UE does not know the preciselocation of the DCI information in a PDCCH, the UE can search and decodethe CCEs in the PDCCH until the DCI is found for the UE's CCs. The PDCCHcandidates for DCI detection can be referred to as a search space. TheUE can find the PDCCH specific to the UE (or the UE's CCs) by monitoringa set of PDCCH candidates (a set of consecutive CCEs on which the PDCCHcould be mapped) in a PDCCH search space in each subframe.

In the 3GPP LTE specification, such as in Release 8, 9, 10, or 11, theUE can use a radio network temporary identifier (RNTI) that can beassigned to the UE by the eNB to try and decode candidates. The RNTI canbe used to demask a PDCCH candidate's cyclic redundancy check (CRC) thatwas originally masked by the eNB using the UE's RNTI. If the PDCCH isfor a specific UE, the CRC can be masked with a UE unique identifier,for example a cell-RNTI (C-RNTI) used in a downlink. If no CRC error isdetected the UE can determine that a PDCCH candidate carries the DCI forthe UE. If a CRC error is detected then the UE can determine that PDCCHcandidate does not carry the DCI for the UE and the UE can increment tothe next PDCCH candidate. The UE may increment to the next PDCCHcandidate in the search space based on the CCE aggregation level (AL).

The number of CCEs used to transmit one piece of control information canbe determined according to the transmission mode, the receiving qualityof the PDCCH allocated to the UE, or the channel quality of the UE, andthe number of CCEs is referred to as a CCE aggregation level, a legacyaggregation level L∈{1,2,4,8}, an enhanced control channel elements(ECCE) aggregation level L∈{1,2,4,8,16,32}, or just aggregation level(AL). The aggregation level can be used to determine the size of asearch space or the number of CCEs (or ECCEs) forming a search space,and/or the number of control channel (CCH) candidates in a search space.The aggregation level of the UE's DCI may not be known at the UE, whichcan be referred to as aggregation level ambiguity. During blinddecoding, the UE may assume an AL. For blind decoding ECCEs, the UE mayalso assume a lowest ECCE value used to transmit DCIs. The lowest ECCEvalue of the DCIs may not be known at the UE, which can be referred toas lowest ECCE ambiguity. The ECCE and an enhanced resource elementgroup (EREG) can be associated with EPDCCH, and CCE and REG can beassociated with PDCCH.

Aggregation level ambiguity (ALA) can cause performance degradation forPDSCH, especially when EPDCCHs are transmitted with PDSCHs. When a UEdetects the UE's DL assignment defining a PDSCH allocation which canoverlap with the PRB pair(s) containing the DL assignment (e.g.,EPDCCH), the UE can assume that the PDSCH scheduled by the DL assignmentis rate-matched around the PRB pair(s) containing the UE's DLassignment, as illustrated in FIG. 3. A resource allocation can includethree PRB pairs (e.g., two contiguous slots). A PRB pair 0 302A caninclude the EPDCCH 320 used to transmit the DCI resource allocation (RA)322 for PRB pair 0, 1, and 2. A PRB pair 1 302B and PRB pair 2 302C caninclude the PDSCH 310A-B.

The rate matching (RM) process can adapt the code rate of the LTE datatransmissions such that the number of information and parity bits to betransmitted matches the resource allocation. For example, based on a 1/3mother code rate of the turbo coder, the LTE rate matching can use acircular buffer to either repeat bits to decrease the code rate orpuncture bits to increase the code rate.

If the DCI indicates PRB 0, 1, 2 are allocated for PDSCH and the DCIitself is detected in PRB 0, UE can rate matching around PRB 0 and mayonly decode PDSCH from PRB 1, 2. One PRB pair may contain 2 or 4 ECCEs.FIG. 4 illustrates an example of four ECCEs (e.g., ECCE 0-4) in one PRBpair (e.g., slot n 120 c and slot n+1 120 d). FIG. 4 illustratesfrequency first sequential mapping of RE across the REs for the ECCEsoccupied by the DCI. The REs for the ECCE can be mapped around thedemodulation reference signals (DMRS). The number labeled in each RE isthe EREG index. In an example, the same EREG index can be used for eachaggregation level. In another example (not shown), time first sequentialmapping of RE across the REs for the ECCEs occupied by the DCI can beused.

FIG. 3 illustrates a challenge due to aggregation level ambiguity. Forlocalized EPDCCH, if both PRB 0 and PRB 1 are allocated for EPDCCHtransmission, and if the eNB uses resource allocation type 0 or 2 toallocate PRB pairs for a UE, the eNB can transmit a DCI with aggregationlevel 4 (AL4) in PRB 0 302A and the UE may successfully decode the DCIwith aggregation level 8 (AL8) from PRB 0 302A and PRB1 302B. With asuccessfully decoded DCI in PRB 0 and PRB1, the UE may assume PRB 0 and1 are used for EPDCCH, so the UE may only try to decode PDSCH from PRB2. So the PDSCH on PRB 1 may not be decoded (e.g., may be lost), so theinformation may need to be resent, which can cause a performancedegradation for the PDSCH.

FIG. 5 illustrates a challenge due to aggregation level ambiguity fordistributed EPDCCH transmission. For distributed EPDCCH transmission,when a number of PRB pairs in one distributed EPDCCH set is greater thana number of EREGs one distributed ECCE contains, the UE can decode theEREGs from the PRB pairs in the one distributed EPDCCH set. For example,as shown in FIG. 5, one EPDCCH set 304 contains eight PRB pairs 302 andone ECCE can contain four EREGs 332 in the EPDCCH 320A-D. If the eNBtransmits DCI with aggregation level 1 (AL1) 332 and UE decodes the DCIsuccessfully, assuming aggregation level 2 (AL2) 334, AL4, or AL8, sincean aggregation level more than AU (e.g., AL2, AL4, or AL8) can occupyall the PRB pairs in the distributed EPDCCH set, then UE can rate matcharound all the PRBs for PDSCH decoding. So the PDSCH 310C-F may not bedecoded (e.g., may be lost), so the information may need to be resent,which can again cause a performance degradation for the PDSCH.

Not only does aggregation level ambiguity present some challenges, butlowest ECCE ambiguity can also generate some inefficiencies in blinddecoding. Based on a legacy definition of PDCCH search space (e.g., asdefined in 3GPP LTE standard Release 8 Technical Specification (TS)36.213), the resources of one aggregation level that the UE monitors forPDCCH blind detection can overlap with the resources of anotheraggregation level. For example, FIG. 6 shows overlapping CCEs, where theUE can monitor CCE {1,2,3,4,5,6} to detect DCI with aggregation level 1and monitor CCE {1&2, 3&4, 5&6} to detect DCI with aggregation level 2.

Since rate matching can be used to generate the DCI, the payloads in CCE2 (AL1 342), in an example, can be an exact repetition of payloads inCCE 1. Similarly, the payloads in CCE 3-4 (AL2 344B), in an example, canbe an exact repetition of payloads in CCE 1-2 (AL2 344A). A lowest CCEindex confusion issue or lowest ECCE ambiguity can result. For legacyPDCCH, padding zero bits can be used to make the payload size of DCI notequal to any one of {12, 14, 16, 20, 24, 26, 32, 40, 44, 56} as in asdefined in 3GPP LTE standard Release 8 TS 36.212. Padding zero bits maynot be available for EPDCCH.

The payload size {12, 14, 16, 20, 24, 26, 32, 40, 44, 56} is optimizedin 3GPP LTE standard Release 8 TS 36.212 with an assumption that CCEsize is 36 REs. However, in the EPDCCH design the ECCE size can bevariable due to different configuration of cell-specific referencesignals (CRS), channel state information reference signals (CSI-RS),and/or legacy control. So the DCI size can be optimized for EPDCCHconsidering different ECCE sizes.

For example, a payload size that can result in aggregation levelconfusion issue can satisfy the criteria represented by n*3/2*k=m*n_cce,where k and m are integers, and m={1 2 4 8 16}, n represents a payloadsize, m represents a number of occupied CCEs, k represents a startingpoint of repetitions of the coded block, n_cce represents a size of anECCE, and n is less than (16−m)*n_cce*2*3/4. The coding rate can be lessthan 3/4; otherwise, the UE may not decode the payload.

Based on the criteria of the example, the payload sizes (e.g., rawpayload size 48 or 28) that can cause aggregation level confusion fordifferent ECCE sizes (e.g., 12, 24, or 33) is illustrated in Table 1.Table 1 illustrates payload sizes that can cause aggregation confusionfor different ECCE sizes (m=1,2,4,8,16).

TABLE 1 Payloads including ECCE Size 16 bits CRC Raw Payload Size 12 6448 24 64 48 33 44 28

To assist in resolving some aggregation level confusion, 3GPP LTEstandard Release 11 (e.g., V11.1.0 (2012-12)) Technical Specification(TS) 36.212 Table 5.3.3.1.2-1 can be modified to include 28 and 48information bits for ambiguous sizes, represented by Table 2.

TABLE 2 {12, 14, 16, 20, 24, 26, 28, 32, 40, 44, 48, 56}

In another example, a forward compatible table to include m=1, 2, 3, . .. , 16, as shown in Table 3, can be used instead of the aggregationlevels the UE monitors (m=1,2,4,8,16). Table 3 illustrates payload sizesthat can cause aggregation confusion for different ECCE sizes (m=1,2,3,. . . , 16). Table 2 is defined including the payload sizes that canlead to aggregation level ambiguity given different aggregation levels.

TABLE 3 ECCE Size Payloads including 16 bits CRC Raw Payload size 11 33,44, 66 17, 28, 50 12 44, 52, 64 28, 36, 48 13 39, 52 23, 36 15 35, 45,50, 55, 65, 70 19, 29, 34, 39, 49, 54 16 64 48 17 34, 51, 68 18, 35, 5218 33, 39, 44, 52, 54, 66 17, 23, 28, 36, 38, 50 19 38, 57 22, 41 21 35,49, 63, 70 19, 33, 47, 54 22 33, 44, 66 17, 28, 50 23 46, 69 30, 53 2444, 52, 64 28, 36, 48 25 50 34 26 39, 52 23, 36 27 33, 39, 45, 54, 63,66 17, 23, 29, 38, 47, 50 28 35 19 29 29, 58 13, 42 30 35, 44, 45, 50,52, 55, 65, 70 19, 28, 29, 34, 36, 39, 49, 54 31 31, 62 15, 46 32 64 4833 33, 44, 55, 66 17, 28, 39, 50 34 34, 51, 68 18, 35, 52 35 35, 50, 7019, 34, 54

Various methods can be used to resolve the aggregation level ambiguityand the lowest ECCE ambiguity. For example, a unique frequency first ortime first sequential mapping across the REs occupied by the DCI may beused for each aggregation level (e.g., alternative one). FIG. 7Aillustrates an EREG index map for an AL 2 354. FIG. 7B illustrates anEREG index map for an AL 1 352. FIG. 4 illustrates an EREG index mapthat can be used for an AL 4 or AL 8. The EREG index map (not shown) canalso use a separate time first sequential EREG index map for AL 1, AL 2,or AL 4 or AL 8.

Instead of mapping modulated symbols to REs in one ECCE and then mappingto REs in another ECCE as used for legacy PDCCH, the eNB can use afrequency first or time first mapping across the REs that are used totransmit the DCI (i.e., mapping across both the ECCE and the EREG).Since each EREG/ECCE can be distributed in one PRB pair, the aggregationlevel mapping can result in different symbol mapping order for differentaggregation levels and different EREGs. Even if repetition exists in theencoded bits (see FIG. 6), the UE may not decode the DCI correctly withan incorrect AL assumption (e.g., resolving AL ambiguity) or incorrectstarting ECCE assumption (e.g., resolving lowest ECCE ambiguity). Usingan aggregation level EREG index map can solves both AL ambiguity andlowest ECCE ambiguity.

In another example, aggregation level ambiguity can be resolved using anaggregation level specific phase shifting for all modulated symbols 470(e.g., alternative two), as illustrated in FIG. 8. FIG. 8 illustratesphysical channel processing 400 for an eNB. As previously discussed, aUE unique identifier, such as a cell-RNTI (C-RNTI), can be used to maskthe DCI. A cyclic redundancy check (CRC) can be used for error detectionin DCI messages. The entire PDCCH payload can be used to calculate a setof CRC parity bits. The CRC parity bits can then be appended to the endof the PDCCH payload. During CRC attachment 430, control information 410(e.g., DCI) for a UE can be masked with the RNTI 432 of the UE.

The RNTI can be used for scrambling the cyclic redundancy check (CRC)attached to a specific DCI format. Cyclic redundancy check (CRC) can bean error detecting code appended to a block of data to be transmitted.The value of the CRC can be calculated from the block of data. Thelength of the CRC can determine the number of errors which can bedetected in the block of data on reception of the data. A CRC may not beable to correct errors or determine which bits are erroneous.

Then the DCI message with the CRC attachment can undergo channel coding,such as tail biting convolutional coding (CC) 440, by a channel encoder.Convolutional coding is a form of forward error correction.Convolutional coding can improve the channel capacity by addingcarefully selected redundant information. For example, LTE can use arate 1/3 tail biting encoder with a constraint length k=7, which meansthat one in three bits of the output contain ‘useful’ information whilethe other two add redundancy. A tail biting convolutional coder caninitialize its internal shift register to the last k bits of the currentinput block, rather than to an ‘all zeros’ state, which means the startand end states can be the same, without the need to zero pad the inputblock. The overhead of ‘terminating’ the coder can be eliminated, so theoutput block can contain fewer bits than a standard convolutional coder.

At the UE, the tail biting convolutional decoder design may be morecomplicated since the initial state may be unknown, but the decoderknows the start and end states are the same. In another example, achannel decoder can be implemented using a Viterbi algorithm.

A rate matching 450 module can create an output bitstream with a desiredcode rate, as previously discussed. A modulator can be used to modulatethe output bitstream. The modulator can use various modulation andcoding schemes (MCS), such as quadrature phase-shift keying (QPSK) 460modulation. Modulation is the process of varying one or more propertiesof a periodic waveform, called the carrier signal, with a modulatingsignal which typically contains information to be transmitted (e.g.,DCI).

A module (e.g., AL specific phase shifter) can provide an aggregationlevel specific phase shifting for all modulated symbols 470. Forexample, AL specific phase shifting can be added in addition to anEPDCCH generation procedure. For instance, if four aggregation levelscan be used for EPDCCH transmission, each AL can be assign one of fourphase shifting factors (e.g., {1 j −1−j}). The eNB can select oneshifting factor according to the aggregation level and multiply on allthe modulated symbols (e.g., QPSK modulated symbols). The phase shiftingfactor can be used to solve the AL ambiguity issue.

In another example, on top of AL specific phase shifting, EREG specificphase shifting for the EREGs within one PRB pair may also be used. TheEREG specific phase shifting for the EREGs can solve the lowest ECCEambiguity issue. The EREG shifting factor can be the same or differentwith aggregation level specific shifting factors.

After aggregation level specific phase shifting, the phase shiftedmodulated symbols can be mapped to resource elements 480 by a mapper onone or various layers (e.g., REs can be shown in FIG. 4).

In another example, aggregation level ambiguity can be resolved using anaggregation level specific scrambling on the uncoded (e.g., raw) DCIbits 420 (e.g., alternative three) using an aggregation level specificscrambler, as illustrated in FIG. 9. FIG. 9 illustrates physical channelprocessing 402 for an eNB. The scrambling sequence can have the samelength as the uncoded DCI bits. For instance, for four aggregationlevels, the sequences could be:

-   [0 0 . . . 0]-   [1 1 . . . 1]-   [0 1 0 1 . . . 0 1]-   [1 0 1 0 . . . 1 0].

Other scrambling sequence patterns (not shown) may also be used. Eachaggregation level (e.g., 1, 2, 4, 8, 16, or 32) can use a different andunique scrambling sequence pattern. After raw DCI bit aggregation levelspecific scrambling 420, the DCI bits can undergo CRC attachment 430 andother physical channel processing 402 operations, as previous described.

In another configuration (e.g., alternative four), for distributedEPDCCH transmission, the AL ambiguity may only occur when the eNBtransmits with AL1 and the UE decodes correctly with AL2, AL4, or AL8,in the case where the number of PRB pairs in the distributed EPDCCH setis greater than number of EREGs one ECCE includes. So two AL specificfactors may be used for distributed EPDCCH transmission (e.g., {1 −1})for phase shifting (e.g., similar to alternative two except the numberof shifting factors) or using two sequences to scramble the DCI (e.g.,similar to alternative three except using two scrambling sequences). Forexample, one of the two scrambling sequences can use an all ‘zero’sequence (e.g., sequence A) and the other scrambling sequence can use anall ‘one’ sequence (e.g., sequence B). Alternative four can combine anduse alternatives two and three. Alternative four can provide complexityreduction optimization for a particular distributed EPDCCH set size. Thevarious alternatives (e.g., alternatives 1, 2, 3, and 4) can also bedirectly applied to both localized and distributed EPDCCH set regardlessof a number of PRB pairs per set and a number of EREGs per ECCE.

In another example, the aggregation level ambiguity or the lowest ECCEambiguity can be resolved using an interleaver 490 after rate matching450 (e.g., alternative five) where DCI bits 422 are provide for CRCattachment 430, as illustrated in FIG. 10. The interleaver can be usedto interleave against a fading phenomenon. To make the UE unable todecode the EPDCCH correctly under an incorrect aggregation levelassumption, a bit level interleaver 490 can be inserted between the ratematching block 450 and modulation block 460, as shown in FIG. 10. Anyinterleaver may be applicable as long as the interleaving destroys anencoding chain if the UE assumes an incorrect aggregation level in blinddecoding. Since the legacy PDCCH can use an interleaver for REGinterleaving, the same interleaver can be reused for simplicity (i.e., asub-block interleaver can be reused). In an example, <NULL> elements atthe output of the interleaver can be removed before modulation.

In another example, the aggregation level ambiguity or the lowest ECCEambiguity can be resolved using an interleaver 492 after modulation(e.g., QPSK 460) (e.g., alternative six), as illustrated in FIG. 11.Similar to alternative five, a symbol level interleaver can be insertedbetween the QPSK 460 modulation block and the symbol to RE mapping block480, as shown in FIG. 11. For example, a sub-block interleaver can bereused. For instance, <NULL> elements at the output of the interleavercan be removed before RE mapping.

Another example provides a method 500 for blind decoding downlinkcontrol information (DCI) from an enhanced physical downlink controlchannel (EPDCCH), as shown in the flow chart in FIG. 12. The method maybe executed as instructions on a machine or computer circuitry, wherethe instructions are included on at least one computer readable mediumor one non-transitory machine readable storage medium. The methodincludes the operation of receiving the EPDCCH from an evolved Node B(eNB) at a user equipment (UE), as in block 510. The operation ofrecursively attempting to decode the DCI from enhanced control channelelements (ECCE) of the EPDCCH from a physical resource block (PRB) pairusing a selected set of enhanced resource element group (EREG) indexmappings for the ECCE until the DCI is successfully decoded, whereineach EREG index mapping is configured for a different aggregation level(AL) follows, as in block 520. The next operation of the method can becorrectly decoding the DCI when the EREG index mapping associated with aspecified aggregation level is used, wherein the specified aggregationlevel is used to encode the DCI, as in block 530.

Each EREG index map can be used to determine which resource elements(RE) in a physical resource block (PRB) pair are associated with eachECCE. For example, the REs of a physical resource block (PRB) pairinclude a block of complex-valued symbols y(0), . . . , y(M_(symb)−1)mapped in sequence starting with y(0) to resource elements (k,l) on anassociated antenna port when the REs are part of the EREGS assigned forthe EPDCCH transmission, where M_(symb) is a number of modulationsymbols to transmit on a physical channel, and the mapping to resourceelements (k,l) on antenna port p is an increasing order of first anindex k and then an index l, starting with a first slot and ending witha second slot in a subframe.

In an example, each ECCE can be distributed with other ECCEs infrequency or time in the PRB pair or multiple PRB pairs or each EREG canbe distributed with other EREGs in frequency or time in the PRB pair ormultiple PRB pairs. The operation of correctly decoding the DCI canfurther include determining the aggregation level, and determining alowest ECCE value.

In another example, the method can further include failing to decode theDCI when an assumed aggregation level differs from an encodedaggregation level. A user equipment (UE) can attempt to decode with aEREG index mapping associated with the assumed aggregation level, andthe encoded aggregation level can be the aggregation level used by anevolved Node B (eNB) to encode the DCI for transmission in the EPDCCH.The method can further include attempting to decode the DCI usinganother EREG index mapping associated with another aggregation level.

Another example provides functionality 600 of computer circuitry of anode operable for mapping resource elements (RE) to enhanced controlchannel elements (ECCE) of an enhanced physical downlink control channel(EPDCCH) based on an aggregation level (AL), as shown in the flow chartin FIG. 13. The functionality may be implemented as a method or thefunctionality may be executed as instructions on a machine, where theinstructions are included on at least one computer readable medium orone non-transitory machine readable storage medium. The computercircuitry can be configured to determine a number of ECCE used totransmit downlink control information (DCI), as in block 610. Thecomputer circuitry can be further configured to determine theaggregation level used to transmit the DCI based on the number of ECCEused to transmit the DCI, as in block 620. The computer circuitry canalso be configured to map resource elements (RE) to enhanced resourceelement groups (EREG) of the ECCE assigned to the DCI using an EREGindex, wherein the EREG index is selected based on a localized EPDCCHtransmission scheme or a distributed EPDCCH transmission scheme, as inblock 630.

In an example, the computer circuitry configured to map the RE can befurther configured to map the RE to a physical resource block (PRB) pairfor a localized EPDCCH transmission scheme using a frequency firstsequential mapping across the REs occupied by the DCI, or map the RE toa plurality of PRB pairs a distributed EPDCCH transmission scheme usinga frequency first sequential mapping across the REs occupied by the DCI,where one DCI for the distributed EPDCCH transmission scheme is carriedusing EREGs from the plurality of PRB pairs. In another example, thecomputer circuitry configured to map the RE can be further configured tomap the RE to a physical resource block (PRB) pair for a localizedEPDCCH transmission scheme using a time first sequential mapping acrossthe REs occupied by the DCI, or map the RE to a plurality of PRB pairs adistributed EPDCCH transmission scheme using a time first sequentialmapping across the REs occupied by the DCI, where one DCI for thedistributed EPDCCH transmission scheme is carried using EREGs from theplurality of PRB pairs.

In a configuration, the ECCE can be transmitted in a physical resourceblock (PRB) pair, where each PRB pair includes four ECCEs or two ECCEs.The REs of a physical resource block (PRB) pair can include a block ofcomplex-valued symbols y(0), . . . , y(M_(symb)−1) mapped in sequencestarting with y(0) to resource elements (k,l) on an associated antennaport when the REs are part of the EREGS assigned for the EPDCCHtransmission, where M_(symb) is a number of modulation symbols totransmit on a physical channel, and the mapping to resource elements(k,l) on antenna port p is an increasing order of first an index k andthen an index l, starting with a first slot and ending with a secondslot in a subframe.

The computer circuitry can be further configured to allocate resource toa physical downlink shared channel (PDSCH) with the EPDCCH allocateresource to a physical downlink shared channel (PDSCH) with the EPDCCH,and transmit the PDSCH in the resource allocation. The EPDCCH can be alocalized EPDCCH or a distributed EPDCCH

FIG. 14 illustrates an example node 710 (e.g., eNB) and an examplewireless device 720 (e.g., UE). The node can include a node device 712.The node device or the node can be configured to communicate with thewireless device (e.g., UE). The node device can include a processor 714and a transceiver 716. The processor 714 and/or transceiver 716 can beconfigured for mapping resource elements (RE) to enhanced controlchannel elements (ECCE) of an enhanced physical downlink control channel(EPDCCH) based on an aggregation level (AL), as described in 600 of FIG.13.

The wireless device 720 (e.g., UE) can include a transceiver 724 and aprocessor 722. The wireless device (i.e., device) can be configured forblind decoding downlink control information (DCI) from an enhancedphysical downlink control channel (EPDCCH), as described in 500 of FIG.12.

Referring back to FIG. 14, the processor 722 can be configured to:Recursively attempt to decode the DCI from enhanced control channelelements (ECCE) of the EPDCCH from physical resource block (PRB) regioncandidates in a PRB set using a selected set of enhanced resourceelement group (EREG) index maps for the ECCE until the DCI issuccessfully decoded; and decode the DCI with an EREG index mapassociated with a same aggregation level used to encode the DCI. EachEREG index map can be configured for a different aggregation level (AL).

Each EREG index map can be used to determine which resource elements(RE) in a physical resource block (PRB) pair are associated with theECCE for aggregation level. For example, the REs of a physical resourceblock (PRB) pair can include a block of complex-valued symbols y(0), . .. , y(M_(symb)−1) mapped in sequence starting with y(0) to resourceelements (k,l) on an associated antenna port when the REs are part ofthe EREGS assigned for the EPDCCH transmission, where M_(symb) is anumber of modulation symbols to transmit on a physical channel, and themapping to resource elements (k,l) on antenna port p is an increasingorder of first an index k and then an index l, starting with a firstslot and ending with a second slot in a subframe.

In another example, the processor 714 can be further configured to failto decode the DCI when an assumed aggregation level differs from anencoded aggregation level. The processor can attempt to decode with aEREG index map associated with the assumed aggregation level, and theencoded aggregation level can be the same aggregation level used by anevolved Node B (eNB) to encode the DCI for transmission in the EPDCCH.

The transceiver 716 can be configured to receive the EPDCCH from a node.The node can include a base station (BS), a Node B (NB), an evolved NodeB (eNB), a baseband unit (BBU), a remote radio head (RRH), a remoteradio equipment (RRE), a remote radio unit (RRU), or a centralprocessing module (CPM).

In another configuration, transceiver 716 can be configured to receive aphysical downlink shared channel (PDSCH) with the EPDCCH in a resourceallocation (RA). The RA is a RA type 0, RA type 1 or a RA type 2 definedin a Third Generation Partnership Project (3GPP) Long Term Evolution(LTE) standard Release 11.

In another example, the same aggregation level is used to encode the DCIin 1, 2, 4, 8, 16, or 32 ECCE. In another configuration, the processorconfigured to decode the DCI can be further configured to resolve anaggregation level ambiguity; and resolve a lowest ECCE ambiguity.

FIG. 15 provides an example illustration of the wireless device, such asa user equipment (UE), a mobile station (MS), a mobile wireless device,a mobile communication device, a tablet, a handset, or other type ofwireless device. The wireless device can include one or more antennasconfigured to communicate with a node or transmission station, such as abase station (BS), an evolved Node B (eNB), a baseband unit (BBU), aremote radio head (RRH), a remote radio equipment (RRE), a relay station(RS), a radio equipment (RE), a remote radio unit (RRU), a centralprocessing module (CPM), or other type of wireless wide area network(WWAN) access point. The wireless device can be configured tocommunicate using at least one wireless communication standard including3GPP LTE, WiMAX, High Speed Packet Access (HSPA), Bluetooth, and WiFi.The wireless device can communicate using separate antennas for eachwireless communication standard or shared antennas for multiple wirelesscommunication standards. The wireless device can communicate in awireless local area network (WLAN), a wireless personal area network(WPAN), and/or a WWAN.

FIG. 15 also provides an illustration of a microphone and one or morespeakers that can be used for audio input and output from the wirelessdevice. The display screen may be a liquid crystal display (LCD) screen,or other type of display screen such as an organic light emitting diode(OLED) display. The display screen can be configured as a touch screen.The touch screen may use capacitive, resistive, or another type of touchscreen technology. An application processor and a graphics processor canbe coupled to internal memory to provide processing and displaycapabilities. A non-volatile memory port can also be used to providedata input/output options to a user. The non-volatile memory port mayalso be used to expand the memory capabilities of the wireless device. Akeyboard may be integrated with the wireless device or wirelesslyconnected to the wireless device to provide additional user input. Avirtual keyboard may also be provided using the touch screen.

Various techniques, or certain aspects or portions thereof, may take theform of program code (i.e., instructions) embodied in tangible media,such as floppy diskettes, compact disc-read-only memory (CD-ROMs), harddrives, non-transitory computer readable storage medium, or any othermachine-readable storage medium wherein, when the program code is loadedinto and executed by a machine, such as a computer, the machine becomesan apparatus for practicing the various techniques. Circuitry caninclude hardware, firmware, program code, executable code, computerinstructions, and/or software. A non-transitory computer readablestorage medium can be a computer readable storage medium that does notinclude signal. In the case of program code execution on programmablecomputers, the computing device may include a processor, a storagemedium readable by the processor (including volatile and non-volatilememory and/or storage elements), at least one input device, and at leastone output device. The volatile and non-volatile memory and/or storageelements may be a random-access memory (RAM), erasable programmable readonly memory (EPROM), flash drive, optical drive, magnetic hard drive,solid state drive, or other medium for storing electronic data. The nodeand wireless device may also include a transceiver module (i.e.,transceiver), a counter module (i.e., counter), a processing module(i.e., processor), and/or a clock module (i.e., clock) or timer module(i.e., timer). One or more programs that may implement or utilize thevarious techniques described herein may use an application programminginterface (API), reusable controls, and the like. Such programs may beimplemented in a high level procedural or object oriented programminglanguage to communicate with a computer system. However, the program(s)may be implemented in assembly or machine language, if desired. In anycase, the language may be a compiled or interpreted language, andcombined with hardware implementations.

It should be understood that many of the functional units described inthis specification have been labeled as modules, in order to moreparticularly emphasize their implementation independence. For example, amodule may be implemented as a hardware circuit comprising customvery-large-scale integration (VLSI) circuits or gate arrays,off-the-shelf semiconductors such as logic chips, transistors, or otherdiscrete components. A module may also be implemented in programmablehardware devices such as field programmable gate arrays, programmablearray logic, programmable logic devices or the like.

Modules may also be implemented in software for execution by varioustypes of processors. An identified module of executable code may, forinstance, comprise one or more physical or logical blocks of computerinstructions, which may, for instance, be organized as an object,procedure, or function. Nevertheless, the executables of an identifiedmodule need not be physically located together, but may comprisedisparate instructions stored in different locations which, when joinedlogically together, comprise the module and achieve the stated purposefor the module.

Indeed, a module of executable code may be a single instruction, or manyinstructions, and may even be distributed over several different codesegments, among different programs, and across several memory devices.Similarly, operational data may be identified and illustrated hereinwithin modules, and may be embodied in any suitable form and organizedwithin any suitable type of data structure. The operational data may becollected as a single data set, or may be distributed over differentlocations including over different storage devices, and may exist, atleast partially, merely as electronic signals on a system or network.The modules may be passive or active, including agents operable toperform desired functions.

Reference throughout this specification to “an example” or “exemplary”means that a particular feature, structure, or characteristic describedin connection with the example is included in at least one embodiment ofthe present invention. Thus, appearances of the phrases “in an example”or the word “exemplary” in various places throughout this specificationare not necessarily all referring to the same embodiment.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary. In addition, various embodiments and example of the presentinvention may be referred to herein along with alternatives for thevarious components thereof. It is understood that such embodiments,examples, and alternatives are not to be construed as defactoequivalents of one another, but are to be considered as separate andautonomous representations of the present invention.

Furthermore, the described features, structures, or characteristics maybe combined in any suitable manner in one or more embodiments. In thefollowing description, numerous specific details are provided, such asexamples of layouts, distances, network examples, etc., to provide athorough understanding of embodiments of the invention. One skilled inthe relevant art will recognize, however, that the invention can bepracticed without one or more of the specific details, or with othermethods, components, layouts, etc. In other instances, well-knownstructures, materials, or operations are not shown or described indetail to avoid obscuring aspects of the invention.

While the forgoing examples are illustrative of the principles of thepresent invention in one or more particular applications, it will beapparent to those of ordinary skill in the art that numerousmodifications in form, usage and details of implementation can be madewithout the exercise of inventive faculty, and without departing fromthe principles and concepts of the invention. Accordingly, it is notintended that the invention be limited, except as by the claims setforth below.

What is claimed is:
 1. At least one non-transitory machine readablestorage medium having instructions embodied thereon for blind decodingdownlink control information (DCI) from an enhanced physical downlinkcontrol channel (EPDCCH), the instructions when executed by one or moreprocessors of a user equipment (UE) perform the following: processing,at the UE, the EPDCCH received from a base station, wherein the EPDCCHincludes the DCI; and attempting one or more times to decode the DCIfrom enhanced control channel elements (ECCE) of the EPDCCH fromphysical resource block (PRB) region candidates in a PRB set using aselected set of enhanced resource element group (EREG) index maps forthe ECCE until the DCI is successfully decoded.
 2. The at least onenon-transitory machine readable storage medium of claim 1, whereinresource elements (REs) of a PRB pair include a block of symbols mappedin sequence to REs on an associated port when the REs of the PRB pairare part of EREGs assigned for the EPDCCH transmission.
 3. The at leastone non-transitory machine readable storage medium of claim 1, furthercomprising instructions which when executed performs the following:decoding the DCI with an EREG index map associated with a sameaggregation level used to encode the DCI.
 4. The at least onenon-transitory machine readable storage medium of claim 1, wherein eachEREG index map is configured for a different aggregation level (AL), andresource elements (REs) of a PRB pair include a block of complex-valuedsymbols y(0), . . . , y(M_(symb)−1) mapped in sequence starting withy(0) to resource elements (k,l) on the associated antenna port when theREs are part of the EREGS assigned for the EPDCCH transmission, whereM_(symb) is a number of modulation symbols to transmit on a physicalchannel, and the mapping to resource elements (k,l) on antenna port p isan increasing order of first an index k and then an index l, startingwith a first slot and ending with a second slot in a subframe.
 5. The atleast one non-transitory machine readable storage medium of claim 1,wherein each EREG index map is used to determine which resource elements(RE) in a physical resource block (PRB) pair are associated with theECCE for aggregation level.
 6. The at least one non-transitory machinereadable storage medium of claim 1, further comprising instructionswhich when executed performs the following: failing to decode the DCIwhen an assumed aggregation level differs from an encoded aggregationlevel, wherein the processor attempts to decode with an EREG index mapassociated with the assumed aggregation level, and the encodedaggregation level is the same aggregation level used by the base stationto encode the DCI for transmission in the EPDCCH.
 7. The at least onenon-transitory machine readable storage medium of claim 1, furthercomprising instructions which when executed performs the following:receiving a physical downlink shared channel (PDSCH) with the EPDCCH ina resource allocation (RA), wherein the RA is a RA type 0, RA type 1, ora RA type 2 defined in a Third Generation Partnership Project (3GPP)Long Term Evolution (LTE) standard Release 11; and rate matching thePDSCH around a physical resource block (PRB) pair including the DCI inthe EPDCCH.
 8. The at least one non-transitory machine readable storagemedium of claim 1, wherein the same aggregation level is used to encodethe DCI in 1, 2, 4, 8, 16, or 32 ECCE.
 9. The at least onenon-transitory machine readable storage medium of claim 1, furthercomprising instructions which when executed performs the following:resolving an aggregation level ambiguity.
 10. The at least onenon-transitory machine readable storage medium of claim 1, furthercomprising instructions which when executed performs the following:resolving a lowest ECCE ambiguity.
 11. A user equipment (UE) operable toblindly decode downlink control information (DCI) from an enhancedphysical downlink control channel (EPDCCH), the UE comprising: atransceiver configured to receive the EPDCCH from a base station,wherein the EPDCCH includes the DCI; and one or more processorsconfigured to attempt one or more times to decode the DCI from enhancedcontrol channel elements (ECCE) of the EPDCCH from physical resourceblock (PRB) region candidates in a PRB set using a selected set ofenhanced resource element group (EREG) index maps for the ECCE until theDCI is successfully decoded.
 12. The UE of claim 11, wherein resourceelements (REs) of a PRB pair include a block of symbols mapped insequence to REs on an associated port when the REs of the PRB pair arepart of EREGs assigned for the EPDCCH transmission.
 13. The UE of claim11, wherein the one or more processors are further configured to decodethe DCI with an EREG index map associated with a same aggregation levelused to encode the DCI.
 14. The UE of claim 11, wherein each EREG indexmap is configured for a different aggregation level (AL), and resourceelements (REs) of a PRB pair include a block of complex-valued symbolsy(0), . . . , y(M_(symb)−1) mapped in sequence starting with y(0) toresource elements (k,l) on the associated antenna port when the REs arepart of the EREGS assigned for the EPDCCH transmission, where M_(symb)is a number of modulation symbols to transmit on a physical channel, andthe mapping to resource elements (k,l) on antenna port p is anincreasing order of first an index k and then an index l, starting witha first slot and ending with a second slot in a subframe.
 15. The UE ofclaim 11, wherein each EREG index map is used to determine whichresource elements (RE) in a physical resource block (PRB) pair areassociated with the ECCE for aggregation level.
 16. The UE of claim 11,wherein the one or more processors are further configured to fail todecode the DCI when an assumed aggregation level differs from an encodedaggregation level, wherein the processor attempts to decode with an EREGindex map associated with the assumed aggregation level, and the encodedaggregation level is the same aggregation level used by the base stationto encode the DCI for transmission in the EPDCCH.
 17. The UE of claim11, wherein: the transceiver is further configured to receive a physicaldownlink shared channel (PDSCH) with the EPDCCH in a resource allocation(RA), wherein the RA is a RA type 0, RA type 1, or a RA type 2 definedin a Third Generation Partnership Project (3GPP) Long Term Evolution(LTE) standard Release 11; and the one or more processors are furtherconfigured to rate match the PDSCH around a physical resource block(PRB) pair including the DCI in the EPDCCH.
 18. The UE of claim 11,wherein the same aggregation level is used to encode the DCI in 1, 2, 4,8, 16, or 32 ECCE.
 19. The UE of claim 11, wherein the one or moreprocessors are further configured to resolve an aggregation levelambiguity.
 20. The UE of claim 11, wherein the one or more processorsare further configured to resolve a lowest ECCE ambiguity.
 21. At leastone non-transitory machine readable storage medium having instructionsembodied thereon for blind decoding downlink control information (DCI)from an enhanced physical downlink control channel (EPDCCH), theinstructions when executed by one or more processors of a user equipment(UE) perform the following: processing, at the UE, the EPDCCH receivedfrom a base station, wherein the EPDCCH includes the DCI; attempting oneor more times to decode the DCI from enhanced control channel elements(ECCE) of the EPDCCH from physical resource block (PRB) regioncandidates in a PRB set using a selected set of enhanced resourceelement group (EREG) index maps for the ECCE until the DCI issuccessfully decoded, wherein the DCI is decoded with an EREG index mapassociated with a same aggregation level used to encode the DCI; andfailing to decode the DCI when an assumed aggregation level differs froman encoded aggregation level, wherein the processor attempts to decodewith an EREG index map associated with the assumed aggregation level,and the encoded aggregation level is the same aggregation level used bythe base station to encode the DCI for transmission in the EPDCCH,wherein resource elements (REs) of a PRB pair include a block of symbolsmapped in sequence to REs on an associated port when the REs of the PRBpair are part of EREGs assigned for the EPDCCH transmission.
 22. The atleast one non-transitory machine readable storage medium of claim 21,wherein each EREG index map is configured for a different aggregationlevel (AL), and resource elements (REs) of a PRB pair include a block ofcomplex-valued symbols y(0), . . . , y(M_(symb)−1) mapped in sequencestarting with y(0) to resource elements (k,l) on the associated antennaport when the REs are part of the EREGS assigned for the EPDCCHtransmission, where M_(symb) is a number of modulation symbols totransmit on a physical channel, and the mapping to resource elements(k,l) on antenna port p is an increasing order of first an index k andthen an index l, starting with a first slot and ending with a secondslot in a subframe.
 23. The at least one non-transitory machine readablestorage medium of claim 21, wherein each EREG index map is used todetermine which resource elements (RE) in a physical resource block(PRB) pair are associated with the ECCE for aggregation level.
 24. Theat least one non-transitory machine readable storage medium of claim 21,further comprising instructions which when executed performs thefollowing: receiving a physical downlink shared channel (PDSCH) with theEPDCCH in a resource allocation (RA), wherein the RA is a RA type 0, RAtype 1, or a RA type 2 defined in a Third Generation Partnership Project(3GPP) Long Term Evolution (LTE) standard Release 11; and rate matchingthe PDSCH around a physical resource block (PRB) pair including the DCIin the EPDCCH.
 25. The at least one non-transitory machine readablestorage medium of claim 21, wherein the same aggregation level is usedto encode the DCI in 1, 2, 4, 8, 16, or 32 ECCE.